Although only a minority of economists support truly open borders, surveys of economists have repeatedly shown that a majority of economists favor more open borders compared to current legal regimes or popular opinion. This is of particular significance in so far as many of the chief arguments against immigration, such as suppression of wages of natives, are arguments whose evaluation is informed by economic theory.

This consensus, to the extent it exists, is not meant to imply that all economists favor more open borders — some, like George Borjas, are more pessimistic about the effect of low-skilled immigration on low-skilled workers in the United States. Further, the claim of consensus made here is meant as a support, rather than as a substitute, for the actual pro-open borders arguments.

• Economic Impacts of Immigration: A Survey – this is an NBER working paper, cited by at least 74 other papers, summarising the state of economic knowledge on the impacts of immigration as of 2011. The paper provides a very broad overview of economic impacts, comprehensively covering the findings of various studies on impacts in areas such as wages and the welfare state. The study’s scope includes both the US and Europe. Overall, it finds:
  “Within the large empirical literature looking at the effects of immigration on native employment and wages, most studies find only minor displacement effects even after very large immigrant flows.”
  “Most empirical studies estimate the fiscal impacts of immigration to be very small… On average, immigrants appear to have a minor positive net fiscal effect for host countries.”
• Open Letter on Immigration addressed to the United States president. The letter was initiated by Alex Tabarrok and David Theroux (see also a discussion of the letter by Alex Tabarrok in an article titled Why Ruin the World’s Best Anti-Poverty Program?). The letter has over 500 signatories, with the majority being economists in the United States. Further, these signatories span the political and ideological spectrum. Apart from the large roster of libertarian economist signatories, the signatories include Gregory Mankiw (former economic policy adviser to George Bush) and Bradford DeLong (progressive economist and blogger).
• According to an AEA survey of 210 randomly selected Ph.D. economists (PDF, 6 pages): “Few economists believe that current U.S. immigration levels are too high (16.7%)—although many (29.5%) are neutral on the matter.” The quote is from Page 4 of the survey.
• What Makes People Think Like Economists? (PDF, 33 pages) by Bryan Caplan: In this document, Caplan notes the results of the Survey of Americans and Economists on the Economy. The survey asks:
  

  Regardless of how well you think the economy is doing, there are always some problems that
  keep it from being as good as it might be. I am going to read you a list of reasons some
  people have given for why the economy is not doing better than it is. For each one, please tell
  me if you think it is a major reason the economy is not doing better than it is, a minor reason,
  or not a reason at all. (0 = Not a reason at all”; 1 = “Minor reason”; 2 = “Major reason”)

  Question 4 of the survey asks people to rate the reason “There are too many immigrants” to which Americans gave a mean response of 1.22 with standard deviation 0.78 whereas economists gave a mean response of 0.20 with standard deviation 0.43.

• Even the economists who oppose immigration (such as George Borjas) generally agree that immigrants do not hurt natives economically on net. Their main economic concerns are modest reductions in the wages and employment prospects of certain segments of the native population, specifically low-skilled natives and in particular high school dropouts. Some economists are also concerned with the immigrants going on welfare objection and with other non-economic impacts of immigration. However, it’s worth noting that the economic impacts that the general public is most worried about are largely rejected even by economists skeptical of immigration.

One criticism of this line of reasoning is that economists’ support for expanded immigration is an instance of the economist blind spot.